Also called "Chat Programs". These applications are installed on a PC by a user, and allow immediate "chats" between other users of the program. Some of these programs also allow audio or video conferencing as well as the ability to execute file transfers.
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Pidgin (formerly known as Gaim) is a multi-protocol instant messaging client for Linux, BSD, Mac OS X, and Windows. It is compatible with AIM (Oscar and TOC protocols), ICQ, MSN Messenger, Yahoo, IRC, Jabber, Gadu-Gadu, and Zephyr networks.
Pidgin users can log in to multiple accounts on multiple IM networks simultaneously.